// Copyright 2016 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/snapshot/partial-serializer.h"
#include "src/snapshot/startup-serializer.h"

#include "src/api-inl.h"
#include "src/math-random.h"
#include "src/microtask-queue.h"
#include "src/objects-inl.h"
#include "src/objects/slots.h"

namespace v8 {
namespace internal {

    PartialSerializer::PartialSerializer(
        Isolate* isolate, StartupSerializer* startup_serializer,
        v8::SerializeEmbedderFieldsCallback callback)
        : Serializer(isolate)
        , startup_serializer_(startup_serializer)
        , serialize_embedder_fields_(callback)
        , can_be_rehashed_(true)
    {
        InitializeCodeAddressMap();
        allocator()->UseCustomChunkSize(FLAG_serialization_chunk_size);
    }

    PartialSerializer::~PartialSerializer()
    {
        OutputStatistics("PartialSerializer");
    }

    void PartialSerializer::Serialize(Context* o, bool include_global_proxy)
    {
        context_ = *o;
        DCHECK(context_->IsNativeContext());
        reference_map()->AddAttachedReference(
            reinterpret_cast<void*>(context_->global_proxy()->ptr()));
        // The bootstrap snapshot has a code-stub context. When serializing the
        // partial snapshot, it is chained into the weak context list on the isolate
        // and it's next context pointer may point to the code-stub context.  Clear
        // it before serializing, it will get re-added to the context list
        // explicitly when it's loaded.
        context_->set(Context::NEXT_CONTEXT_LINK,
            ReadOnlyRoots(isolate()).undefined_value());
        DCHECK(!context_->global_object()->IsUndefined());
        // Reset math random cache to get fresh random numbers.
        MathRandom::ResetContext(context_);

#ifdef DEBUG
        MicrotaskQueue* microtask_queue = context_->native_context()->microtask_queue();
        DCHECK_EQ(0, microtask_queue->size());
        DCHECK(!microtask_queue->HasMicrotasksSuppressions());
        DCHECK_EQ(0, microtask_queue->GetMicrotasksScopeDepth());
        DCHECK(microtask_queue->DebugMicrotasksScopeDepthIsZero());
#endif
        context_->native_context()->set_microtask_queue(nullptr);

        VisitRootPointer(Root::kPartialSnapshotCache, nullptr, FullObjectSlot(o));
        SerializeDeferredObjects();

        // Add section for embedder-serialized embedder fields.
        if (!embedder_fields_sink_.data()->empty()) {
            sink_.Put(kEmbedderFieldsData, "embedder fields data");
            sink_.Append(embedder_fields_sink_);
            sink_.Put(kSynchronize, "Finished with embedder fields data");
        }

        Pad();
    }

    void PartialSerializer::SerializeObject(HeapObject obj)
    {
        DCHECK(!ObjectIsBytecodeHandler(obj)); // Only referenced in dispatch table.

        if (SerializeHotObject(obj))
            return;

        if (SerializeRoot(obj))
            return;

        if (SerializeBackReference(obj))
            return;

        if (startup_serializer_->SerializeUsingReadOnlyObjectCache(&sink_, obj)) {
            return;
        }

        if (ShouldBeInThePartialSnapshotCache(obj)) {
            startup_serializer_->SerializeUsingPartialSnapshotCache(&sink_, obj);
            return;
        }

        // Pointers from the partial snapshot to the objects in the startup snapshot
        // should go through the root array or through the partial snapshot cache.
        // If this is not the case you may have to add something to the root array.
        DCHECK(!startup_serializer_->ReferenceMapContains(obj));
        // All the internalized strings that the partial snapshot needs should be
        // either in the root table or in the partial snapshot cache.
        DCHECK(!obj->IsInternalizedString());
        // Function and object templates are not context specific.
        DCHECK(!obj->IsTemplateInfo());
        // We should not end up at another native context.
        DCHECK_IMPLIES(obj != context_, !obj->IsNativeContext());

        // Clear literal boilerplates and feedback.
        if (obj->IsFeedbackVector())
            FeedbackVector::cast(obj)->ClearSlots(isolate());

        // Clear InterruptBudget when serializing FeedbackCell.
        if (obj->IsFeedbackCell()) {
            FeedbackCell::cast(obj)->set_interrupt_budget(
                FeedbackCell::GetInitialInterruptBudget());
        }

        if (SerializeJSObjectWithEmbedderFields(obj)) {
            return;
        }

        if (obj->IsJSFunction()) {
            // Unconditionally reset the JSFunction to its SFI's code, since we can't
            // serialize optimized code anyway.
            JSFunction closure = JSFunction::cast(obj);
            closure->ResetIfBytecodeFlushed();
            if (closure->is_compiled())
                closure->set_code(closure->shared()->GetCode());
        }

        CheckRehashability(obj);

        // Object has not yet been serialized.  Serialize it here.
        ObjectSerializer serializer(this, obj, &sink_);
        serializer.Serialize();
    }

    bool PartialSerializer::ShouldBeInThePartialSnapshotCache(HeapObject o)
    {
        // Scripts should be referred only through shared function infos.  We can't
        // allow them to be part of the partial snapshot because they contain a
        // unique ID, and deserializing several partial snapshots containing script
        // would cause dupes.
        DCHECK(!o->IsScript());
        return o->IsName() || o->IsSharedFunctionInfo() || o->IsHeapNumber() || o->IsCode() || o->IsScopeInfo() || o->IsAccessorInfo() || o->IsTemplateInfo() || o->IsClassPositions() || o->map() == ReadOnlyRoots(startup_serializer_->isolate()).fixed_cow_array_map();
    }

    namespace {
        bool DataIsEmpty(const StartupData& data) { return data.raw_size == 0; }
    } // anonymous namespace

    bool PartialSerializer::SerializeJSObjectWithEmbedderFields(Object obj)
    {
        if (!obj->IsJSObject())
            return false;
        JSObject js_obj = JSObject::cast(obj);
        int embedder_fields_count = js_obj->GetEmbedderFieldCount();
        if (embedder_fields_count == 0)
            return false;
        CHECK_GT(embedder_fields_count, 0);
        DCHECK(!js_obj->NeedsRehashing());

        DisallowHeapAllocation no_gc;
        DisallowJavascriptExecution no_js(isolate());
        DisallowCompilation no_compile(isolate());

        HandleScope scope(isolate());
        Handle<JSObject> obj_handle(js_obj, isolate());
        v8::Local<v8::Object> api_obj = v8::Utils::ToLocal(obj_handle);

        std::vector<EmbedderDataSlot::RawData> original_embedder_values;
        std::vector<StartupData> serialized_data;

        // 1) Iterate embedder fields. Hold onto the original value of the fields.
        //    Ignore references to heap objects since these are to be handled by the
        //    serializer. For aligned pointers, call the serialize callback. Hold
        //    onto the result.
        for (int i = 0; i < embedder_fields_count; i++) {
            EmbedderDataSlot embedder_data_slot(js_obj, i);
            original_embedder_values.emplace_back(embedder_data_slot.load_raw(no_gc));
            Object object = embedder_data_slot.load_tagged();
            if (object->IsHeapObject()) {
                DCHECK(isolate()->heap()->Contains(HeapObject::cast(object)));
                serialized_data.push_back({ nullptr, 0 });
            } else {
                // If no serializer is provided and the field was empty, we serialize it
                // by default to nullptr.
                if (serialize_embedder_fields_.callback == nullptr && object->ptr() == 0) {
                    serialized_data.push_back({ nullptr, 0 });
                } else {
                    DCHECK_NOT_NULL(serialize_embedder_fields_.callback);
                    StartupData data = serialize_embedder_fields_.callback(
                        api_obj, i, serialize_embedder_fields_.data);
                    serialized_data.push_back(data);
                }
            }
        }

        // 2) Embedder fields for which the embedder callback produced non-zero
        //    serialized data should be considered aligned pointers to objects owned
        //    by the embedder. Clear these memory addresses to avoid non-determism
        //    in the snapshot. This is done separately to step 1 to no not interleave
        //    with embedder callbacks.
        for (int i = 0; i < embedder_fields_count; i++) {
            if (!DataIsEmpty(serialized_data[i])) {
                EmbedderDataSlot(js_obj, i).store_raw(kNullAddress, no_gc);
            }
        }

        // 3) Serialize the object. References from embedder fields to heap objects or
        //    smis are serialized regularly.
        ObjectSerializer(this, js_obj, &sink_).Serialize();

        // 4) Obtain back reference for the serialized object.
        SerializerReference reference = reference_map()->LookupReference(reinterpret_cast<void*>(js_obj->ptr()));
        DCHECK(reference.is_back_reference());

        // 5) Write data returned by the embedder callbacks into a separate sink,
        //    headed by the back reference. Restore the original embedder fields.
        for (int i = 0; i < embedder_fields_count; i++) {
            StartupData data = serialized_data[i];
            if (DataIsEmpty(data))
                continue;
            // Restore original values from cleared fields.
            EmbedderDataSlot(js_obj, i).store_raw(original_embedder_values[i], no_gc);
            embedder_fields_sink_.Put(kNewObject + reference.space(),
                "embedder field holder");
            embedder_fields_sink_.PutInt(reference.chunk_index(), "BackRefChunkIndex");
            embedder_fields_sink_.PutInt(reference.chunk_offset(),
                "BackRefChunkOffset");
            embedder_fields_sink_.PutInt(i, "embedder field index");
            embedder_fields_sink_.PutInt(data.raw_size, "embedder fields data size");
            embedder_fields_sink_.PutRaw(reinterpret_cast<const byte*>(data.data),
                data.raw_size, "embedder fields data");
            delete[] data.data;
        }

        // 6) The content of the separate sink is appended eventually to the default
        //    sink. The ensures that during deserialization, we call the deserializer
        //    callback at the end, and can guarantee that the deserialized objects are
        //    in a consistent state. See PartialSerializer::Serialize.
        return true;
    }

    void PartialSerializer::CheckRehashability(HeapObject obj)
    {
        if (!can_be_rehashed_)
            return;
        if (!obj->NeedsRehashing())
            return;
        if (obj->CanBeRehashed())
            return;
        can_be_rehashed_ = false;
    }

} // namespace internal
} // namespace v8
